has anyone built the XOno?
I wonder how it compares to the pearl 2. i love the pearls sound signature though. sounds natural and cozy, well defined. good stereo image..
i'm still wishing it produced a little less noise though -
as a high gain-level unit, i imagine that's hard. been tinkering with my pearl 2 trying to get the noise floor lower.. so far no changes really. i supose i could always get into step up transformers.. just feel like my unit is producing bit more noise than it ought to. i have young ears, and it can be heard at higher volume levels from the seating position... especially at night.
part of me wonders if i had mis installed the jfets and didnt get the 4 matched .. so i did a little swapping and no real improvement.
been using a koetsu black - much less noise than the fidelity research cart due to the koetsus higher output. man that cart is sweet.
I wonder how it compares to the pearl 2. i love the pearls sound signature though. sounds natural and cozy, well defined. good stereo image..
i'm still wishing it produced a little less noise though -
as a high gain-level unit, i imagine that's hard. been tinkering with my pearl 2 trying to get the noise floor lower.. so far no changes really. i supose i could always get into step up transformers.. just feel like my unit is producing bit more noise than it ought to. i have young ears, and it can be heard at higher volume levels from the seating position... especially at night.
part of me wonders if i had mis installed the jfets and didnt get the 4 matched .. so i did a little swapping and no real improvement.
been using a koetsu black - much less noise than the fidelity research cart due to the koetsus higher output. man that cart is sweet.
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You could boost the transconductance by lowering the degeneration in the input stage which would shave off most part of the source resistors Johnson contribution also. But such an action would demand a redesign of values for the bias voltage supply. More current leading to more drop etc. That would add more gain and maybe change the THD a little too. A partial redesign of the front end in other words and you should know what you are doing, else let it be as is.
The Koetsu Black is nice, has that Koetsu bit "technicolor" signature, but I remember it somewhat less "airy" in the brilliance range (upper treble) also.
The Koetsu Black is nice, has that Koetsu bit "technicolor" signature, but I remember it somewhat less "airy" in the brilliance range (upper treble) also.
congrats on your completed project!
i love the case you found. i imagine your really enjoying the benefits of the external power supply.
how do you find the noise level on it now? im having a hard time discerning if my unit is producing more noise than it should or not. some people seem to say they need to put their ears right up to the tweeters to hear noise at volume... at half volume i can hear mine hiss from my chair. ..and i can kinda hear it in the music a weee bit in quiet parts
how's the noise on yours?
Thanks Salas!
Judging by my partial understanding of that fine suggestion, i'll have to leave it to the master chefs - as i'm only a cook. without a recipe, I'm flying blind! makes me wish id chosen engineering over Pharm!
do you think the use of metal foil resistors in the input would have any advantage?
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Where, under the fets? Or as as R19//20 input load? Maybe you could prefer them subjectively as load resistors but noise contribution wise no, when having metal film already I presume.
In the normal gain mode it is inaudible even with my line stage turned up to "rattle the windows "level. When I switch in the 300-Ohm resistor for high gain mode it has a little hiss with no music but as soon as the needle drops the vinyl noise swamps the preamp noise. On my test bench I measured 69db weighted ref 5mv input/ normal gain and 58db s/n, ref 500uV in, high-gain mode.
69/58 does not really look impressive. Would this figure be typical for all Pearl 2's? Mine is a bit noisier (just hiss, no hum) than the built in phono of my Sony TA-FA70es which is spec'ed at 78 (MC)/87(MM) and has higher gain. I think it's the only thing I would like to see improved on the Pearl 2. The sound is great and in practice the noise does not really matter as the groove noise from the record is far higher.
Hi Wellerman,
I measured the Pearl with my test bench setup that is not real quiet. I have lots of EMI and RFI in my area. I am never able to duplicate the published specs for phono stages. My analyzer is a Sound Technology 1500A that was designed for tape deck analysis. It is a nice old beast but is nowhere near as quiet as my previous HP distortion analyzer but it is infinitely more versatile. I basically use it to confirm if something is broken or not.
Again, the Pearl is very quiet in my Living Room setup. It is definitely quieter that the Threshold FET 9 phono stage that it replaced. The FET 9 was rated at -80db ref 1mV input. So if the Pearl was measured the same way I would assume that it is > -80db S/N. I have an Audio Precision Portable 1 at work. I'll have to take the Pearl in sometime and measure it on that.
I measured the Pearl with my test bench setup that is not real quiet. I have lots of EMI and RFI in my area. I am never able to duplicate the published specs for phono stages. My analyzer is a Sound Technology 1500A that was designed for tape deck analysis. It is a nice old beast but is nowhere near as quiet as my previous HP distortion analyzer but it is infinitely more versatile. I basically use it to confirm if something is broken or not.
Again, the Pearl is very quiet in my Living Room setup. It is definitely quieter that the Threshold FET 9 phono stage that it replaced. The FET 9 was rated at -80db ref 1mV input. So if the Pearl was measured the same way I would assume that it is > -80db S/N. I have an Audio Precision Portable 1 at work. I'll have to take the Pearl in sometime and measure it on that.
Hi 6L6, and Hifi-Hospital.
No hum. It's white noise - the expected sort...but it seems like there is wee too much of it. (hiss)
It had me wondering about the input FETs... id suspected that i might have mixed up the quad-matched sets. so, i rotated a two from the left to the right board - Even after swapping a pair around, no real difference.
At high gain (~72db) and at 50% on the Rotel preamp, the pearl is hissing enough to differentiate it from lp-noise in quiet passages in the music. With the needle off the record and the preamp at 100% its hissing as loud as a faucet spouts water.
how easy is it to fry the FETS? I tried to be swift when installing them... maybe i heated them too much/long.
i'll be able to tinker some more in a couple weeks. have some exams to write and work in the way at the moment. Just want to gather some ideas about what it could be.
In Pearl 2 pdf document, its designer recommended dual bridge type of power supply(one diode bridge for each polarity).
But in Pass Labs flagship factory made phono stages XP-15 and XP-25, according to high res. photos , they have ordinary single bridge PS !
XP-15 PS it is not even dual mono. Very unusual for the high end phono stages.
But in Pass Labs flagship factory made phono stages XP-15 and XP-25, according to high res. photos , they have ordinary single bridge PS !
XP-15 PS it is not even dual mono. Very unusual for the high end phono stages.
I'm sure Wayne knows what he is doing -- I see a very nice shielded transformer, and a single bridge with snubber. Then massive, multiple RC stages of filtering. Once that 'raw' DC powersupply is sent to the dual-mono RIAA sections, there are regulators on each rail of each channel, a capacitance multiplier or two, and huge amounts of local decoupling for each stage.
What strikes me is that there is more PSU capacitance in this photo than a Firstwatt power amp!
Also consider that with a single transformer it is going to be much easier to control the magnetic and mechanical hum than with 2.
What strikes me is that there is more PSU capacitance in this photo than a Firstwatt power amp!
Also consider that with a single transformer it is going to be much easier to control the magnetic and mechanical hum than with 2.
An externally hosted image should be here but it was not working when we last tested it.
Transformer is not shielded, take look at the top clear coated internal wires.
With the existing transformer with center tap, it is possible to use four diode bridges for each channel, or without CT configuration as in Pearl2.
Pass Aleph Ono, Xono, XP-15, and XP-25 all use single bridge and center taped transformers for raw PS and brute force filtering.
With the existing transformer with center tap, it is possible to use four diode bridges for each channel, or without CT configuration as in Pearl2.
Pass Aleph Ono, Xono, XP-15, and XP-25 all use single bridge and center taped transformers for raw PS and brute force filtering.
The transformer is shielded, look at the metal band around it's circumference, and the violet (purple) lead coming out of the transfomer and attached to AC mains earth.
On a toroid... interesting. How exactly is that constructed???? Screens like that are usually found on EI transformers.
That's a potted, or encapsulated transformer. That potting material happens to be polyamide, not a metal for screening...